Force adjustment in impact printers

ABSTRACT

A plurality of self-restoring equally spaced apart print hammers selectively are driven lineally toward a printing position by continuously rotating impellers having equiangularly spaced radial impelling elements. Each impeller is effective through the agency of a rockable interponent, which is selectively elevated into the path of associated impelling elements upon latching of the armature of an electromagnet, for transmitting impeller force to a corresponding print hammer. An elastomeric bumper, disposed in the path of the print hammers, dampens printing force on dies, which are conveyed past said hammers for printing, in equally spaced relationship different from the spacing of said hammers. Each die, when at a printing station, is aligned with a print hammer but spaced therefrom a distance inversely proportional to its printing area for producing copy of uniform intensity.

United States Patent [191 Babler July 16, 1974 I FORCE ADJUSTMENT INIMPACT PRINTERS [75] Inventor: Egon S. Babler, Northbrook, Ill. [73]Assignee: Teletype Corporation, Skokie, Ill.

[22] Filed: July 3, 1972 -[2l] Appl. No.: 268,237

[52] US. Cl. .101/93 C, 101/111 [51] Int. Cl B41j9/l2 [58] Field ofSearch 101/93 C, 111, 368;

[56] References Cited UNITED STATES PATENTS 2,796,966 6/1957 Toeppen;197/17 3,144,821 8/1964 Drejza 101/93 C 3,172,353 3/1965 101/93 C3,266,419 8/1966 Erpel et a1. 1'01/93 C 3,308,749 3/1967 Dowd 101/368 X3,386,376 6/1968 Mutz et al lOl/93 C 3,451,335 6/1969 Cunningham 101/111X 3,504,623 4/1970 Staller 101/93 C 3,587,456 6/1971 Jaensch l0l/93 C3,742,848 7/1973 l-luntoon et a1 -10l/l 11 X OTHER PUBLICATIONS Bear eta1., Printl-Iammer Impact Control Mechanism," IBM Technical DisclosureBulletin, Vol. 5, No. 11, Apr., 1963, pp. 27-29.

Primary Examiner-Robert E. Pulfrey Assistant Examiner-Edward M. CovenAttorney, Agent, or FirmSherman P. Appel; John L. Landis [57] ABSTRACT Aplurality of self-restoring equally spaced apart print hammersselectively are driven lineally toward a-printing position bycontinuously rotating impellers having equiangularly spaced radialimpelling elements. Each impeller is effective through the agency of arockable interponent, which is selectively elevated into the path 27Claims, 4 Drawing Figures PATENTEnJuu 61974 BACKGROUND OF THE INVENTIONprint hammers which are actuated by a logic system responsive to data tobe reproduced.

Ideally suited for developing impact forces in said class of printers,because of the high level of timing accuracy for print hammer control,are impelling means of the type disclosed in US. Pat. No. 2,927,960,issued to W. P. Byrnes, Mar. 8, 1960. In my copending application Ser.No. 286,238, filed contemporaneously herewith, there is shown anddescribed an improvement for adapting the disclosure of said patent forhigh speed printing.

Heretofore unknown for printers with such impelling means areymechanismsfor varying the printing forces .such that image density issubstantially uniform from one print-out period to another, regardlessof the: (l) number of copies (within limits) simultaneously printedduring eachprint-out period and (2) variation in the .masses'of printingdies within a font.

It is an object of the present invention to provide an improved impactprinter. v 7 I It is another object of. the invention inan impactprinter to adjust the printing forces in accordance with the number ofplies simultaneously being printed.

It is afurther obje ct of the-invention in an impact printer to adjustprinting forces according to the masse of the printing dies.

SUMMARY OF THE INVENTION Toattain the foregoing, and other objects ofthe invention which'will become apparent from the ensuing FIG. 2' is avertical sectional view of said printer according to the line 22 of FIG.I;

FIG. 3 is an enlarged elevational view of a print hammer for saidprinter; and

FIG. 4 is a detailed view taken in a horizontal plane according to theline 4-4 of FIG. 2, parts having been omitted for the purpose ofillustration.

DETAILED DESCRIPTION OF THE INVENTION Referring now to FIG. 1 of thedrawings, the impact printer shown is generally designated 10. It has apair of spaced apart pulleys 12 and 14 about which an endless carrier 16is trained for translocating a plurality of pallets 18 by movement in acircuitous path. A plurality of dies 17 (FIG. 2) are carried on thefront faces of the pallets, the latter being uniformly dimensioned anduniformlyand equally spaced apart axially of the carrier. When the diescomprise alphanumeric characters, two or more successive fonts axiallyof carrier 16 may enable longer line output.

Carrier 16 and pallets 18, together with their mountings may besubstantially as shown and described in the copending application ofFrancis E; I-Iuntoon and James F. Kearney, Ser. No. 208,198, filed Dec.15, 1971, and assigned to the assignee of the present application, nowPat.- No. 3,742,848, granted July 3, 1973.

In accordance with said last copending application, the

plane in which parallel axes of pulleys l2 and 14 are disposed and thevertical section 20 of web 22 on which printing is about to occur areorthogonally disposed. Such arrangement generates a loop in the carrierwith an upper or printing course 21 and a lower or return course 23which are disposed in a plane which is substantially parallel to websection 20.

In the exemplary printer 10,.pulley 12 is an idler I sheave while pulley14 is a drive sheave secured to a shaft 24, Driving torque continuouslyis transmitted to saidj shaft from an operating prime mover means,

- direction indicated by arrow 31 during printer operadetaileddescriptiomin a printer which has means for selectively driving a printhammer in a lineal path between a non-printing position and a printingposition. A carrier and the hammer are relatively movable forsuccessively aligning carrier supported dies with-the hammer forprinting. The impact of the hammer is adjusted according to the depth ofmaterial against which the impact is applied, the. adjustment resultingfrom means for damping the driving force and disposed in the path of thehammer.

From another aspect, the objects of the invention are attained in animpact printer in which printing is effected by aligning a succession ofdies with impact means. In such printer. means are provided for varyingthe printing force applied to the dies at the time of printing accordingto their printing areas.

BRIEF DESCRIPTION OF THE DRAWINGS In the ensuing detailed description ofthe drawings, reference is had to the accompanying drawings on which:

'FIG. 1 is a perspective view of an impact printer embodying one form ofthe invention, parts being broken away and parts omittedfor the purposeof illustration;

herein shown as a motor 26, through a drive train generally designated28. The latter hereinincludes an impeller shaft 30. This shaft iscontinuously driven in'the tion.

A segment 32 of ribbon 34 is disposed in'a plane substantially parallelto carrier course 21 between and spaced slightly from face 36 of websection 20 and the 1 pallets 18 supported from said last course. Theribbon is trained abouta plurality of ribbon guides 38 which are spacedapart such that the ribbon assumes a generally rectangular configurationin a horizontal plane. Opposed end'portions of the ribbon are secured toa pair of adjoining ribbon spools 40 and 42 which alter nately functionfor; ribbon supply and accumulation. They alternately are driven inopposite angular directions, by a spool control mechanism 44, thedetails of construction of which form no part of the present invention.Mechanism 44 is connected to motor 26 through a pulley wheel 46,disposed in a common plane 3 vention. Thereupon, operating means, beinga drive train generally designated 54, advances web 22, in the directionshown by arrow 56, a line at a time such advancement results fromincremental rotation of a worm gear 58 for driving a pulley belt 60intermittently angularly to move a cylindrical roller 62. Roller 62 isdisposed'transversely of and adjacent to the path of web movement forfrictionally engaging web 22 and incooperation with other components(not shown), intermittedly drawing said web from its supply source (notshown) about a guiding cylinder 64, as said web is advanced.

Impelling means comprises an array of radially symmetrical impellers 66(only representative ones of which are shown in FIG. 1). The impellingmeans herein are substantially as shown and described in my aforesaidcopending applications Ser. No. 268,238 and in another application Ser.No. 268,236, also filed contemporaneously herewith. Accordingly, eachimpeller is comprised of a plurality of raidal, equiangularly spacedarms or impelling elements 68, the impellers being concentricallysecured to shaft 30 for rotation therewith in the direction shown byarrow 70 (FIG. 2),

in the exemplary embodimentQTheimpellers are axially or horizontallyspaced such that each is disposed in substantially horizontal alignmentwith a printing station on an imaginary line extending horizontallyacross web section 20. Opposed end portions of the shaft 30 arejournalled in spaced apart vertical side members 72 '(only one isshown'in FIG. 2) of the frame or chassis.

74 of printer 10.

Impacter means for printing comprise a plurality of hammers 76 (onlysome of which are shown in FIG. 1) having enlarged printing heads 77 attheir inner ends,

' the heads 77 being-disposed behind back face 78 (FIG.

2) of web section 20. As shown in FIG. 4, each hammer is aligned withthe others in a horizontal array parallel to the alignment of impellers66 for linear reciprocating movement along a horizontal printing axis X,toward and away from an associated type die 17. As illustrated in FIGS.3 and 4, the printing axes X refer to horizontal axes runninglongitudinally through the centers of the hammers 76, from left to rightin those FIGS, and

through the center of the type dies 17 when aligned witha hammer forprinting, as shown in FIG. 3 and as shown for the first, third and fifthdies 17 from the top in FIG. 4. Each hammer also is aligned with, thoughspaced'from, and disposed out of the path of movement of an associatedimpeller by which it can be selectively driven in a lineal path alongprinting axis X, perpendicularly to web section 20, between a normal ornonprinting position (FIG. 1) and a printing position (dashed line ofFIG. 4) in which the hammer head 77 engages against said back face 78(FIG. 2).

The dies-17 on pallets 18 in course 21 and hammers v76 are disposed at acommon horizontal level; and said pallets and their dies whentranslocated move in a path parallel to the hammer array for printing.Thereby,

each-palletl8 and-groups thereof can be moved successively into printingpositions in horizontalalignment with successive hammers 76 and groupsthereof, along printing axes X. The force generated by each impeller 66for urging web section 20, ribbon'segment 32 and any aligned dies 17into contact is of sufficient magnitude for printing by forming an imageof each such die on web face 78. In the exemplary embodiment of theinvention, the hammersare associated with and reciprocatively arrangedin chassis 74 by means and in the manner disclosed in said copendingapplication Ser. No. 268,238. As described in that application, and asshown in this application each hammer 76 is elongated in the directionof its line of flight (axis X), and includes a rectangular body section176, having the head section 77 formed at the inner or right end, asviewed in FIGs. 3 and 4, and having a relatively long, relatively thin,rectangular tail section 177 formed at the outer or left-end of the bodysection 176, and extending toward the associated impeller 66, asillustrated in FIG. 2. The outer or left end 178 of the tail section 177is flattened as shown in FIGS. 1 and 4 for driving by one of theimpeller arms 68 to propel the hammer 76, as will be explainedhereafter. As. illustrated in FIGS. 3 and 4, the hammer sections 77, 176and 177 will extend in a straight horizontal line centered on theprinting axis X.

, are slideably mounted in the chambers 182 against a transverse bearingbar 183 mounted on the wall 180'. A chassis plate 184 has portionsdisposed in bearing engagement with hammers76 and extends in ahorizontal plane as a roof or cover for chamber 182. A slotted flange(not shown) depends from the plate 184 to provide horizontally alignedverticalguide slots between which the hammers are reciprocative, asshown and described in-the copendingapplication Ser. No. 268,238. Theseguide members in the frame serve to mount and guide the hammers 76 forprecise linear reciprocation along the printing axes X, to printcharacters as will be described hereafter.

A horizontal bumper in the form of an elongated rod is disposed parallelto shaft 30 along a horizontal axis Y (FIGS. 1 and 4) perpendiculartohammer axes X, and has opposed ends secured in the chassis sides 72.Said rod extends through horizontally aligned holes or slots 82 in thehammers 76 for limiting horizontal hammer movementalong axis X, asillustrated in FIGS.

2 and 3, theslots are generally rectangular as viewed in the plane ofFIGS. 2 and 3, and extend through the body section section 176 of eachhammer in the' direction of bumper axis Y. (The bumper axis Y refers tothe perpendicular horizontal aixs running through the center of thebumper 80, from top to bottom in the layout of FIG. 4, or from lefttoright in FIG. 1.)

As shown in FIGS. 3 and 4, the bumper 80 has a portion receivedwithin'the slot 82 of each hammer 76 in the row, and the height ofthe-bumper 80 (from top to bottom in FIG. 3) is less than that of theslots 82 so that the hammers 76 may reciprocate with respect to thebumper along theprinting axis X. However, the portion of the bumper 80within each slot 82 is enclosed on all sides by walls of the slot 82, asshown in FIGS. 1 and 3, the slot 82 and body section 176 of the hammerbeing symmetrical above and below axis X, as viewed in the verticalplane of FIG. 3, so that the bumper is centered on axis X as is theslot82. t A leaf spring 84- (FIG. 2) of general vertical orientation andassociated with each hammer 76, is included in hammer driving means. Ithas a lower end portion which is rigidly secured to a front chassisplate 86 and an upper end portion engaged in a downwardly opening Eachhammer head 77 is also formed with an upwardly opening slot 89 (FIGS. 3and '4) aligned with the slot 88 and of the same shape so that thehammer 76 is symmetrical above and below axis X, as viewed in FIG. 3.

Each spring 84 has a slightly tensioned condition (FIG.

' 2) during which its hammer is in its rearward or most remotenon-printing position, and a most tensioned condition (not shown) duringprinting for urging or restoring its hammer to non-printing position.

' Each impeller 66 is adapted to move a printingly associated andaligned hammer 76 through the agency of an interponent 90. In thepreferred embodiment of the invention, printing is effected and theassemblies of the interponents as well as the other parts of printer 10,including means for controlling and liberating the interponents are, asshown and described in said last named copending application. Inaccordance therewith, the interponents are disposed in generalhorizontal alignment and each has: (I) a first'or upper position inwhich it is in a projected condition, with its upper free end portiondisposed inthe path of movement of associated impelling elements 68 fortransmitting force from its impeller 66 to an aligned hammer 76 inconse- -slot 88in the printing head 77 of each hammer 76.

As shown in said I-Iuntoon-Kearney patent pallets 18 are mounted on theinner ends of shanks 100; and the shanks are disposed in a horizontalplane and are removably mounted in carrier 16, extending transverelythrough its hammer proximate side 102 and hammer distal side 104. Inaccordance with the present invention, for adjusting the impact of eachhammer 76 upon printing according to the depth of material against whichthe impact is applied, damping means is disposed in the path of hammermovement. Herein, said last means comprises a resilient or a viscousdamper which may be an elastomer from which bumper 80 is fabricated.Thereby, the hammers and said damping means are arranged for relativemovement. The disposition of the bumper in the hammer slot 82 is suchthat the bumper limits movement of each hammer in each of oppositedirections along printing axis X by engagement with front and rear sides106 and 108 (FIG. 3) of slots 82. In the initial or nonprinting positionof the hammer 76 ,the leaf spring 84 biases the'hammer to the left inFIGS. 3 and 4 to a rest position where the inner or front sidewall 106of the slot 82 engages an inner or front wall 1090f the bumper, as shownin FIGs. 2 and. 3.

quence of which printing occurs, and (2) a lower, nonprinting, 'orsecond position in which said interponent has fallen and is removed fromthe impeller path.

As shown and described in said application Ser. No. 268,238, eachinterponent 90 intermittently is controlled by an electromagnet assemblycomprised of a magnetically latchable armature 92 and an electromagnet94 (FIG. 2). Any suitable logic (not shown and formingno part of thepresent invention) which may be conventional may be employed forenergizing each of said electromagnets 94 selectively. In consequence ofenergization of any electromagnet its armature will be rocked,magnetomotively, against the restoring bias of its spring96 clockwisefrom its position shown (FIG. 2)

j to a latched position (not shown).

Correspondingly, an affected interponent will be thrust upwardly (fromits FIG. 2 position) into its first position or projected condition (notshown) between a pair of adjoining impelling elements 68 against the lowering bias of an associatedspring 98 which becomes tensioned upon upwardmovement of its interponent. Ensuingly, the upwardly thrust interponentwill be en: gaged by a circuitously traveling impelling element 68 androcked into engagement with an' associated hammer 76 to effect momentumtransfer and translation of impeller torque into a lineal force forprinting. In the exemplary printer 10, both momentum transfer andrestoration of an interponent to its second position (FIG. 2) followingmomentum transfer, as well as the conditioning of interpo nents90 forrepeat cycles are as shown and described in said last named copendingapplication.

In the printer 10, as illustrated (FIG. 4), the hammers 76 are equallyspaced apart and the pallets 18 in a font in course21 are also equallyspaced apart. However, the spacing between the centers of thehammers isnot the same as the spacing between the centers of the pallets. Theirspacing, as well as their dimensions, mode and sequence of operations,and printing with printer are as shown and described in said copendingapplication Ser. Nos. 268,238 and 268,236

As best illustrated in FIGS. 2 and 3, the slot 82 is elongated along theX axis, compared with the width of the bumper (from left to right inFIG. 3), so that a preset clearance or distance 110 is provided betweenthe slot and bumper along the axis X of hammer flight. Morespecifically, the distance 110 between the rear wall 112 of bumper 80and each rear side 108 of a slot 82, when its hammer 76 is in its normalposition (FIG.

3) is such that, for the thickest number of plies of sheets of paperintended to be accommodated in the horizontal span 113, between the endface 114 of hammer head 77 and a die 17 aligned therewith for printing,side 108 will just come into engagement with wall 113, when said hammerface reaches printing position. Accordingly, to the extent that thethickness of the paper mass in span 112 is reduced from such maximum,each hammer 76 will move further to the right (relative to FIGS. 2and3), compressing the bumper 80 correspondingly, to reach printingposition shown in phantomlines for the second hammer 76 from the top inFIG. 4. By fabricating bumper 80 of polyurethane material having adu'rometer Shore hardness of A,

Additionally, the bumper 80 is proportioned such that it serves toabsorb rebound energy of the hammers 76 following printing as they arerestored to normal positions (FIG. 1). As each hammer 76 rebounds to theleft in FIGs. 3 and 4 from a printing operation, the inner or right sidewall 106 of the slot 82 engages the inner or right side wall of thebumper 80 to absorb and dampen rebound energy, and thus facilitatereturnof the hammer 76 to the initial position resting against the bumper 80,by the biasing spring 84.

For adjusting the spacing of hammers 76 and pallets 18, that is, forsetting the distance across span 113, the pallets are adjustable towardand away from thehammers. To that end a back-up bar or stop member 116is supported from a frame or chassis member 18 along side 104 of carriercourse 21. The back-up bar is engaged by the outer ends of shanks insaid upper course and is adjustable in a horizontal plane towardand-away from carrier 16 within the limits of a slot 120 in said back-upbar. Means for releaseably securing'the back-up bar in adjustedpositions may comprise a threaded pin 122 passed through slot 120 frommember 118 for holding a clamping nut 124 against the back-up bar.

From another aspect of the invention, the impact upon printing isadjusted according to the force transfer areas or sizes of the printingsurfaces of the printing dies. This adjustment is for minimizingvariation in copy intensity due to variation in the size of charactersof the dies. For that purpose, the lengths of shanks 100 are variedaccording to the sizes of the printing surfaces of dies 17. If it isimpractical to vary the. lengths according to the size of the printingsurface of each die, the variation may be according to sizes withinselected ranges. Herein, three pallet groups 18A, 18B, and 18C are shown(FIG. 4). EAch group has a range of die sizes different from the sizeranges of the others. Pallets 18 having dies whose sizes orprintingareas are within the smallest range have the shortest shanks 100A. In analphanumeric font, punctuation marks such as a period, and a colonbelong in this last-named range. Dies whose printing areas are withinthe greatest size range have the longest shanks 100C. Examples ofalphanumeric characters in this last named range are capitals M and W.Dies within the intermediate size range, such as many lowercase letters,have shanks 1008 of intermediate length.

Accordingly, a hammer 76 which is impelled toward a pallet carried on ashank 100A will travel the greatest distance for printing. Such hammerwill compact the greatest damping mass in bumper 80. Consequently,

when it strikes for printing, its impact force will be less than theimpact force when printing with a die on a pallet carried on either ashank 1008 or 100C; and such force will be dissipated over an area inthe smallest range. On the other hand, a hammer printing with a die ona'shank 100C will travel the least distance to printing position. Suchhammer encounters less damping mass in bumper 80 before reachingprinting position that a hammer printing with a die carried on either ashank 100A or 1008. Such hammer will have the greatest energy on impact;however, such force will be dissipated over a printing surface in thegreatest range.

7 As many modifications in the described construction could beconceived, and-as many widely different embodiments could bemade withoutdeparting from the spirit and scope of the claims, it is intended thatall matter contained in the accompanying specification shall beconsidered as illustrative only and not in a limiting creasing theprinting impact of said hammer as the distance ofhammer movement alongthe lineal path increases comprising:

a slot, having a front'and a rear side, formed in the 6 hammer; andmeans, disposed in and completely surrounded by the slot and engageablewith the rear side of the slot as the hammer is driven in the linealpath toward the printing position, for damping the printing impact ofthe hammer so that the printing impact decreases as the distance ofhammer movement along the lineal path increases and for absorbingrebound energy by engagement with said front side of the slot uponhammer movement to a non-printing position following printing.

2. A combination according to claim 1 characterized by means foradjusting the spacing of said hammer and an aligned die.

3. A combination according to claim 2 characterized by means for movingsaid carrier in a circuitous path, and means for adjusting said diestransversely of said carrier toward and away from said hammer.

4. A combination according to claim 3 wherein said carrier has a hammerproximate side and a hammer distal side, and said adjusting meanscomprises an adjustable stop fixed adjacent said carrier at said distalside for limiting the adjustment of said dies on said carrier.

5. A combination accoding to claim 1 characterized means for moving saidcarrier longitudinally past said hammer to successively align carriersupported dies with said hammer for printing, said carrier havinghammer-distal and hammer proximate sides;

a plurality of pallets, transverse to and slidably supported by thecarrier and having a first end adjacent the hammer proximate side of thecarrier and a second end adjacent the hammer distal side of the carrier,the dies being secured to the first end and the spacing between the diesand the hammer being adjustable by sliding the pallets transversely ofthe carrier; and

a stop member, releasably secured parallel to the carrier along thehammer distal side thereof, for engaging the second end portions of thepallets to restrain the pallets from sliding transversely of the carrierand maintain the spacing of the dies and the hammer during printing.

6. A combination according to claim 1, includingv means for spacing saiddies, when aligned for printing,

varying distances from said hammer.

7. A'combination according to claim 6 wherein said dies comprise aplurality of groups of different lengths, and the Spacing means includesmeansfor spacing each group from said carrier a distance different fromthe spacing of any other group.

8. A combination according to claim 6 wherein each die, when aligned forprinting, is spaced from said hammer a distanceinversely proportional tothe printing surface area of the character on each die to be printed.

9. In a printer of the type wherein printing is effected by driving animpacting means toward a selected one of a plurality of dies, each diehaving a printing surface area, a mechanism for increasing the impactforce of the-impacting means on the selected die as the printing surfacearea of the selected die increases comprising:

a carrier spaced from the impacting means and arranged for a relativemovement therewith; a plurality of die shanks mounted in and extendingfrom the carrier for supporting the plurality of dies, the length of thedie shanks being variable and set in accordance with the printingsurface area of the die carried on each die shank; and

means for decreasing the distance between the impacting means and theselected die as the printing surface area of the selected die increasesso that the impact force on the selected die is increased as theprinting surface area of the selected die increases.

10. In a printer of the type including means means for propelling aprint hammer toward a selected one of a number of type dies to effect aprinting operation, and means, engageable with a portion of the hammeras the hammer is propelled toward a type die, for damping the velocityof the print hammer prior to impact with the type die to absorb some ofthe hammer energy prior to printing, the improvement wherein:

the propelling means is arranged for propelling the hammer toward thetype die with the same velocity regardless of the type character to beprinted; and

11. A printer as recited in claim 10, wherein: the

means for propelling includes means for initially positioning the hammerin the same position prior to propelling,regardless of the typecharacter to be printed;

and

the means for damping includes a resilient bumper mounted in the printerfor engaging a portion of the hammer prior to printing impact so as toabsorb hammer energy and thus decelerate the hammer prior to printing,and means for setting the distance traveled by the hammer after strikingthe bumper and before impact with the type die in accordance with thetype face area, so that the hammer travels the least distance beforeimpact with a die of the largest area, and travels greater distancesbefore impacting with dies of smaller area. l 12. A printer as recitedin claim 11,;wherein th damping means includes means for settingthe-distance between the type dies and the bumper in accordance withtype face area so that the dies with the smallest printing area arepositioned furthest from the bumper inthe printing position.

13. A printer as recited in claim 12, whereinthe type dies are formed atthe inner ends of type support members, and further comprising: i

a continuously traveling endless carrier mounted in the printer foradvancement past the hammer, and carrying the type members so that thetype dies face the hammer and continuously travel past the hammer inalignment therewith for printing; and a fixed back-up member mounted inthe printer so that portions of the type support members travel alongand engage the back-up member as they travel past the hammer, the typesupport members being formed of different lengths in accordance withtype face area, so that the die faces are variably spaced from thebumper as they advance into the printing position aligned with thehammer. 14. A printer as recited in calim 13:

10 wherein the type members comprise type pallets havingelongated'shanks with the type diesformed at inner ends thereof. theshanks comprising the type support members and being mounted in theendless carrier for advancement past the hammer so that the type diesface the hammer; wherein the back-upmember comprises a fixed backup barmounted parallel to the bumper and engaging the outer ends of theshanks; and

wherein the pallet shanks are made in different lengths in accordancewiththe type face area of the particular die carried by the pallet.

15. A printer as recited in claim 10, wherein the propelling meanscomprises:

means for mounting the hammer for free linear reciprocating movementalong a line of flight toward and away from a type die in printingposition, so that an inner printing end of the hammer faces the type dieand an outer end extends away from the type die along the line offlight;

means for initially biasing the hammer to a fixed initial rest positionspaced from the type die; in which the hammer occupies the same initialpostion regardless of the character to be printed; and

means for striking the inner end of the hammer when it is desired toprint a character, with a force sufficient to propel the hammer towardthe type die to print the character. I 16. A printer as recited in claim15, further comprising; v

an endless carrier for the type dies; means for mounting a font of typedies on the carrier for continuous movement past the line of flight andin intermittent momentary alignnment with the inner end of the hammer;and

means for positioning the type dies on the carrier so that the faces ofthe dies are spaced variable distancesfrom the hammer in the initialposition, the spacing being set in accordance with the printing surfacearea of each die in the font so that those dies with the largest areaare positioned closest to the hammer and those with the smallest areaare spaced furthest from the hammer.

17. In combination with a teleprinter. of the type having a chassis, aresilient bumper mounted in the chassis along an axis Y, and a printhammer reciprocable along a printing axis X to engage a type member toprint a character and arranged so that a portion of the print hammerstrikes the bumper to dampen the hammer energy prior to impact with thetype member, an improved hammer assembly characterizedby:

the hammer having a slot extending therethrough parallel to the Y axisand centered on the printing aixs X, the hammer being mounted on thebumper so that portions of the bumper extend through the slot and arecentered on the printing axis X, the slot being formed so that theportions of the bumper within the slot are enclosed on all sides bywalls of the slot and the hammer slot reciprocates on the bumperalongaxis X as the hammer travels to and a from theprinting position, theslot being elongated with respect to the bumper along the X axis so thatfront and rear walls of the slot permit a predetermined length ofreciprocation of the hammer with respect to the bumper. 18. Ateleprinter assembly as recited in claim 17, further comprising:

means for biasing the hammer to an initial nonprinting position wherethe front wall of the slot engages and is stopped by a front wall of thebumper, the bumper having resilient front and rear walls engageablealternately with the front and rear walls of the slot. 19. A teleprinteras recited in claim 17, wherein the hammer rebounds after printing andwherein the front wall of the slot strikes the front wall of the bumperon rebound to dampenthe hammer rebound energy, the bumper havingresiliant front and rear walls engageable alternately with the front andrear walls of the slot.

20..A teleprinter as recited in claim 17, further comprising: 7

means for mounting the hammer in the chassis for linear reciprocatingmovement along the printing axis X, axis X being a linear axisperpendicular to the bumper axis Y and passing through the center of thebumper. 21. A teleprinter assembly as recited in claim 20, wherein thehammer is symmetrical about the axis X in a plane through the X axisperpendicular to the Y axis.

22. A teleprinter assembly as recited in claim 21, further comprising:

means for biasing the hammer to an initial nonprinting position wherethe front wall of the 'slot engages and is stopped by a front wall ofthe bumper, the bumper having resilient front and rear walls engageablealterantely with the front and rear wallsof the slot; and 1 wh'ereinthefront wall of the slot strikes the front wall of the bumper as thehammer rebounds after printing, to dampen the hammerrebound energy.

23. In a teleprinter assembly as recited in claim 17,

of the type wherein the print hammer is propelled toward a slected oneof a number of type dies to effect a printing operation, the improvementfurther characterized by:

means for propelling the hammer toward the type die with the sameinitial velocity regardless of the type character to be printed; theburnper being positioned sothat the rear wall of the slot engages therear wall of the bumper prior to printing impact so as to absorb hammerenergy and thus decelerate the hammer prior to printing; and

v means for setting the distance traveled by the hammer after strikingthe bumper and before impact with the type die. in accordance with thetype face area, so that the hammer travels the least distance beforeimpact with a die of the largest area, and travels greater distancesbefore impacting with dies of amaller area.

24. A teleprinter assembly as recited in claim 17, further comprising: I

means for mounting the hammer in the chassis for free linearreciprocating movement along the printing axis X toward and away from atype member in printing position aligned with the hammer along axis X,so that an inner printing end of the hammer faces the type die and anouter end extends away from the type die along the axis X;

means for biasing the hammer to a fixed initial rest position spacedfrom the type member, in which the front wall of the slot engages and isstopped by the front wall of the bumper; and

means for striking the inner end of the hammer when it is desiredtoprint a character, with a force sufficient to propel the hammer towardthe type die so that the rear wall of the slot engages the rear wall ofthe bumper to dampen the hammer velocity but so that the hammercontinues moving into engagement with the type member to print acharacter.

25. A teleprinter assembly as recited in claim 24,

wherein the means for striking comprises:

a constantly rotating impeller wheel mounted parallel to the hammeralong an axis parallel to the bumper axis Y, the impeller wheel havingprojections. that rotate past the outer end of the hammer out ofengagement therewith; and

an interponent selectively insertable between an oncoming projection ofthe impeller wheel and the inner end of ,thehammer so that theprojection strikes the interponent and forces it aganist the outer endof the hammer to propel the hammer linearly along the printing axis.

26. A teleprinter assembly as recited in'claim 17, wherein the hammercomprises: I

an elongated body section extending linearly along and centered on the Xaxis, the slot being formed along a portion of the body section;

an enlarged head section at-the inner end of the body section andextending therefrom along the X axis toward a type member to be printed,the body section being relatively small in cross section compared'to thehead section; and i an elongated tail section at the outer end of thebody section and extending therefrom along the axis X away from the typemember, the tail section being relatively small in cross sectioncompared to the head section.

27.'ln combination with a teleprinter of the type having a printhammerlinearly reciprocable along a printing axis X to engage a typemember to print a character and arranged so that a portion of the printhammer strikes a resilient bumper to dampen hammer energy prior toimpact with the type member, an improved hammer assembly comprising: ian elongated body section extending linearly alon and centered on the Xaxis, the body section having a slot therethrough centered on andperpendicular to the X axis, in which the, bumper is received so thatthe hammer can reciprocate with respect to the bumper, the slot having arear wall which strikes the bumper to dampen the hammer energy;

away from the type'member, the tail section being relatively small incross section compared to the head section.

1. In a printer having means for selectively driving a print hammer formovement in a lineal path between a non-printing position and a printingposition, and a carrier arranged with said hammer for relative movementto successively align carrier supported dies with said hammer forprinting by impact with force generated against an aligned die by saidhammer, means for decreasing the printing impact of said hammer as thedistance of hammer movement along the lineal path increases comprising:a slot, having a front and a rear side, formed in the hammer; and means,disposed in and completely surrounded by the slot and engageable withthe rear side of the slot as the hammer is driven in the lineal pathtoward the printing position, for damping the printing impact of thehammer so that the printing impact decreases as the distance of hammermovement along the lineal path increases and for absorbing reboundenergy by engagement with said front side of the slot upon hammermovement to a non-printing position following printing.
 2. A combinationaccording to claim 1 characterized by means for adjusting the spacing ofsaid hammer and an aligned die.
 3. A combination according to claim 2characterized by means for moving said carrier in a circuitous path, andmeans for adjusting said dies transversely of said carrier toward andaway from said hammer.
 4. A combination according to claim 3 whereinsaid carrier has a hammer proximate side and a hammer distal side, andsaid adjusting means comprises an adjustable stop fixed adjacent saidcarrier at said distal side for limiting the adjustment of said dies onsaid carrier.
 5. A combination accoding to claim 1 characterized by:means for moving said carrier longitudinally past said hammer tosuccessively align carrier supported dies with said hammer for printing,said carrier having hammer distal and hammer proximate sides; aplurality of pallets, transverse to and slidably supported by thecarrier and having a first end adjacent the hammer proximate side of thecarrier and a second end adjacent the hammer distal side of the carrier,the dies being secured to the first end and the spacing between the diesand the hammer being adjustable by sliding the pallets transversely ofthe carrier; and a stop member, releasably secured parallel to thecarrier along the hammer distal side thereof, for engaging the secondend portions of the pallets to restrain the pallets from slidingtransversely of the carrier and maintain the spacing of the dies and thehammer during printing.
 6. A combination according to claim 1, includingmeans for spacing said dies, when aligned for printing, varyingdistances from said hammer.
 7. A combination according to claim 6wherein said dies comprise a plurality of groups of different leNgths,and the spacing means includes means for spacing each group from saidcarrier a distance different from the spacing of any other group.
 8. Acombination according to claim 6 wherein each die, when aligned forprinting, is spaced from said hammer a distance inversely proportionalto the printing surface area of the character on each die to be printed.9. In a printer of the type wherein printing is effected by driving animpacting means toward a selected one of a plurality of dies, each diehaving a printing surface area, a mechanism for increasing the impactforce of the impacting means on the selected die as the printing surfacearea of the selected die increases comprising: a carrier spaced from theimpacting means and arranged for a relative movement therewith; aplurality of die shanks mounted in and extending from the carrier forsupporting the plurality of dies, the length of the die shanks beingvariable and set in accordance with the printing surface area of the diecarried on each die shank; and means for decreasing the distance betweenthe impacting means and the selected die as the printing surface area ofthe selected die increases so that the impact force on the selected dieis increased as the printing surface area of the selected die increases.10. In a printer of the type including means means for propelling aprint hammer toward a selected one of a number of type dies to effect aprinting operation, and means, engageable with a portion of the hammeras the hammer is propelled toward a type die, for damping the velocityof the print hammer prior to impact with the type die to absorb some ofthe hammer energy prior to printing, the improvement wherein: thepropelling means is arranged for propelling the hammer toward the typedie with the same velocity regardless of the type character to beprinted; and the damping means is arranged for damping the hammervelocity varying amounts to reduce the printing energy varying amountsas a function of the size of the printing surface area on the die of theselected type character to be printed, so that the velocity is dampedmost and the least energy is exerted against dies having the leastprinting surface area.
 11. A printer as recited in claim 10, wherein:the means for propelling includes means for initially positioning thehammer in the same position prior to propelling, regardless of the typecharacter to be printed; and the means for damping includes a resilientbumper mounted in the printer for engaging a portion of the hammer priorto printing impact so as to absorb hammer energy and thus decelerate thehammer prior to printing, and means for setting the distance traveled bythe hammer after striking the bumper and before impact with the type diein accordance with the type face area, so that the hammer travels theleast distance before impact with a die of the largest area, and travelsgreater distances before impacting with dies of smaller area.
 12. Aprinter as recited in claim 11, wherein th damping means includes meansfor setting the distance between the type dies and the bumper inaccordance with type face area so that the dies with the smallestprinting area are positioned furthest from the bumper in the printingposition.
 13. A printer as recited in claim 12, wherein the type diesare formed at the inner ends of type support members, and furthercomprising: a continuously traveling endless carrier mounted in theprinter for advancement past the hammer, and carrying the type membersso that the type dies face the hammer and continuously travel past thehammer in alignment therewith for printing; and a fixed back-up membermounted in the printer so that portions of the type support memberstravel along and engage the back-up member as they travel past thehammer, the type support members being formed of different lengths inaccordance with type face area, so that the die faces are variablyspaced from the bumper as they advance into The printing positionaligned with the hammer.
 14. A printer as recited in calim 13: whereinthe type members comprise type pallets having elongated shanks with thetype dies formed at inner ends thereof, the shanks comprising the typesupport members and being mounted in the endless carrier for advancementpast the hammer so that the type dies face the hammer; wherein theback-up member comprises a fixed back-up bar mounted parallel to thebumper and engaging the outer ends of the shanks; and wherein the palletshanks are made in different lengths in accordance with the type facearea of the particular die carried by the pallet.
 15. A printer asrecited in claim 10, wherein the propelling means comprises: means formounting the hammer for free linear reciprocating movement along a lineof flight toward and away from a type die in printing position, so thatan inner printing end of the hammer faces the type die and an outer endextends away from the type die along the line of flight; means forinitially biasing the hammer to a fixed initial rest position spacedfrom the type die, in which the hammer occupies the same initial postionregardless of the character to be printed; and means for striking theinner end of the hammer when it is desired to print a character, with aforce sufficient to propel the hammer toward the type die to print thecharacter.
 16. A printer as recited in claim 15, further comprising: anendless carrier for the type dies; means for mounting a font of typedies on the carrier for continuous movement past the line of flight andin intermittent momentary alignnment with the inner end of the hammer;and means for positioning the type dies on the carrier so that the facesof the dies are spaced variable distances from the hammer in the initialposition, the spacing being set in accordance with the printing surfacearea of each die in the font so that those dies with the largest areaare positioned closest to the hammer and those with the smallest areaare spaced furthest from the hammer.
 17. In combination with ateleprinter of the type having a chassis, a resilient bumper mounted inthe chassis along an axis Y, and a print hammer reciprocable along aprinting axis X to engage a type member to print a character andarranged so that a portion of the print hammer strikes the bumper todampen the hammer energy prior to impact with the type member, animproved hammer assembly characterized by: the hammer having a slotextending therethrough parallel to the Y axis and centered on theprinting aixs X, the hammer being mounted on the bumper so that portionsof the bumper extend through the slot and are centered on the printingaxis X, the slot being formed so that the portions of the bumper withinthe slot are enclosed on all sides by walls of the slot and the hammerslot reciprocates on the bumper along axis X as the hammer travels toand from the printing position, the slot being elongated with respect tothe bumper along the X axis so that front and rear walls of the slotpermit a predetermined length of reciprocation of the hammer withrespect to the bumper.
 18. A teleprinter assembly as recited in claim17, further comprising: means for biasing the hammer to an initialnonprinting position where the front wall of the slot engages and isstopped by a front wall of the bumper, the bumper having resilient frontand rear walls engageable alternately with the front and rear walls ofthe slot.
 19. A teleprinter as recited in claim 17, wherein the hammerrebounds after printing and wherein the front wall of the slot strikesthe front wall of the bumper on rebound to dampen the hammer reboundenergy, the bumper having resiliant front and rear walls engageablealternately with the front and rear walls of the slot.
 20. A teleprinteras recited in claim 17, further comprising: means for mounting thehammer in the chassis for linear reciprocating movement along theprinting aXis X, axis X being a linear axis perpendicular to the bumperaxis Y and passing through the center of the bumper.
 21. A teleprinterassembly as recited in claim 20, wherein the hammer is symmetrical aboutthe axis X in a plane through the X axis perpendicular to the Y axis.22. A teleprinter assembly as recited in claim 21, further comprising:means for biasing the hammer to an initial nonprinting position wherethe front wall of the slot engages and is stopped by a front wall of thebumper, the bumper having resilient front and rear walls engageablealterantely with the front and rear walls of the slot; and wherein thefront wall of the slot strikes the front wall of the bumper as thehammer rebounds after printing, to dampen the hammer rebound energy. 23.In a teleprinter assembly as recited in claim 17, of the type whereinthe print hammer is propelled toward a slected one of a number of typedies to effect a printing operation, the improvement furthercharacterized by: means for propelling the hammer toward the type diewith the same initial velocity regardless of the type character to beprinted; the bumper being positioned so that the rear wall of the slotengages the rear wall of the bumper prior to printing impact so as toabsorb hammer energy and thus decelerate the hammer prior to printing;and means for setting the distance traveled by the hammer after strikingthe bumper and before impact with the type die in accordance with thetype face area, so that the hammer travels the least distance beforeimpact with a die of the largest area, and travels greater distancesbefore impacting with dies of amaller area.
 24. A teleprinter assemblyas recited in claim 17, further comprising: means for mounting thehammer in the chassis for free linear reciprocating movement along theprinting axis X toward and away from a type member in printing positionaligned with the hammer along axis X, so that an inner printing end ofthe hammer faces the type die and an outer end extends away from thetype die along the axis X; means for biasing the hammer to a fixedinitial rest position spaced from the type member, in which the frontwall of the slot engages and is stopped by the front wall of the bumper;and means for striking the inner end of the hammer when it is desired toprint a character, with a force sufficient to propel the hammer towardthe type die so that the rear wall of the slot engages the rear wall ofthe bumper to dampen the hammer velocity but so that the hammercontinues moving into engagement with the type member to print acharacter.
 25. A teleprinter assembly as recited in claim 24, whereinthe means for striking comprises: a constantly rotating impeller wheelmounted parallel to the hammer along an axis parallel to the bumper axisY, the impeller wheel having projections that rotate past the outer endof the hammer out of engagement therewith; and an interponentselectively insertable between an oncoming projection of the impellerwheel and the inner end of the hammer so that the projection strikes theinterponent and forces it aganist the outer end of the hammer to propelthe hammer linearly along the printing axis.
 26. A teleprinter assemblyas recited in claim 17, wherein the hammer comprises: an elongated bodysection extending linearly along and centered on the X axis, the slotbeing formed along a portion of the body section; an enlarged headsection at the inner end of the body section and extending therefromalong the X axis toward a type member to be printed, the body sectionbeing relatively small in cross section compared to the head section;and an elongated tail section at the outer end of the body section andextending therefrom along the axis X away from the type member, the tailsection being relatively small in cross section compared to the headsection.
 27. In combination with a teleprinter of the type having aprint hammer linearly reciprocAble along a printing axis X to engage atype member to print a character and arranged so that a portion of theprint hammer strikes a resilient bumper to dampen hammer energy prior toimpact with the type member, an improved hammer assembly comprising: anelongated body section extending linearly along and centered on the Xaxis, the body section having a slot therethrough centered on andperpendicular to the X axis, in which the bumper is received so that thehammer can reciprocate with respect to the bumper, the slot having arear wall which strikes the bumper to dampen the hammer energy; anenlarged head section at the inner end of the body section and extendingtherefrom along the axis X toward a type member to be printed, the bodysection being relatively small in cross section compared to the headsection; and an elongated tail section at the outer end of the bodysection and extending therefrom along the axis X away from the typemember, the tail section being relatively small in cross sectioncompared to the head section.